Moss Motors, Ltd

Motorbill,

Well, I've replaced the rotors, repacked the bearings (they look okay, by the way), replaced suspension bushings, and of course the rebuilt calipers. I took a test drive, but cut it short because it started to snow, and everything seems okay.  I looked the entire system over, as you suggested, and didn't see anything unusual.  The pedal is still softer than I would like, but I'm going to take it to a shop and have it bled.  One thing that I did notice, though.  The disc pads seem to be dragging a bit.  You know what I mean?  They don't retract fully from the rotor's surface.  Is that a concern?

zach

zach,

Pads usually have a slight contact with the rotor. New pads need to be bedded in before you can judge. When I install pads for a customer I like to take the car out and go through the "green fade" process for them. This consists of driving the car up to about fifty five MPH or so and braking pretty hard down to about fifteen. Then I repeat the process three or four more times in rapid succession. At the end of this you'll usually smell that new pad hot smell. Then I drive the car about five or six miles and park it. After this, the pads will have begun to break in and seat correctly.

Once they have broken in they should not impart so much drag that the wheel is hard to spin when off the ground, but there will be enough drag that the wheel won't just spin for a minute. It will stop after one or two revolutions. The definitive test is heat. Try to drive ten miles without using the brakes much at all. Then pull over. The rotors shouldn't be radiating much heat at all. If they are, something's not right. Hope this helps. 

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill

Gonna frame that description.

One other idea.  Make sure the master cylinder is installed flush and tight to the servo.

Make that two ideas and a comment. Was the push rod adjusted correctly?

Comment: a rebored/overbored master cylinder will give you a different ratio between the master cylinder and brake cylinders which may give you a different pedal feel.

 

LCJUTILA 

LCJUTILA,

answer (s) 1 Nonadjustable pushrod. 2 original size master, or, if refinished it's within a couple of thousandths of original. I'm waithing until he's broken them in. On servo Bs I've noticed a big difference after bedding in.

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Thanks, Motorbill.  I'll "bed them in", drive them a bit, and get back to you.

zach

Motorbill,

Took her out to set in the pads, and after the second stop, the right front brake started locking up again!  After all I have replaced, I'm at a loss as to what can be causing this.  My frustration level is at a new high!  All of the metal lines look good, the rubber hoses are new...could it be a blockage in the line to the right front. And if so, how would I check that out and how would I clear it?

zach

zach,

This is frustrating and downright weird. If I suspected the line, I wouldn't try to correct it. I'd just replace it. Try breaking it loose at both ends and blowing through it. After clearing out the fluid it should pass air very easily. Jeez, I wish I were there or you were here with the car. There is something fundamental here that is being missed. Brakes and suspension on these cars are just not all that complex. When I get back to the shop on Monday I'll try to remember to look in the manual and at the two Rubber Bumper Bs in the shop right now for a little "outside the box" thinking session. Spring is here. You should be driving this car instead of scratching your head. If it's any comfort, we have temperatures in the low thirties and light snow here in Fort Collins today...

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Guys-

There is something floating around in that right brake line or maybe now in the caliper acting as a check valve intermittently. I've had this problem.

You put your foot on the brake and the pressure  pushes the debris off the blockage point.  Pedal off, debris moves back to block. Pressure builds intermittently depending on how that piece of junk is floating around until the caliper locks. In the olden days when I was in the biz you would often see rubber brake lines that were pristine on the outside and filled with a mysterious mud-like substance on the inside. When you are the second or third owner of a car you have no idea of the maintenance or lack thereof that the car has had or the knowledge or the competence of the mechanics that worked on it previously.   Especially in a British car. The brake fluid should be, in my opinion (especially in a damp climate), purged completely every 12-18  months. Brake fluid is much less expensive than brake parts.

I hope this solves it.

I feel your frustration.

LCJUTILA 

LCJ,

New brake flex hoses, new fluid,(lot's of it.) If you have time, read the entire series. It's worth it for the mystery alone.

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill and brake problem person 

 

I think you're smelling the same check-valve rat. It's got the symptoms. It's just a matter of it's location. Somewhere between the master cylinder and the right front caliper.  The warped rotors and pedal pulse were cause by overheating because of the pads binding. (You knew that)  These secondary symptoms are clouding the issue. Man, I could tell you about what happened to me with this type of problem but it would take two pages! Almost as long as a brake bleeding demonstration...

 

LCJUTILA 

People-

How crazy is this?! I'm answering my own response!  How about the PRESSURE DIFFERENTIAL WARNING SWITCH? The thing gets cocked off to one side  and starts fouling the whole thing up .. Some previous owner has a problem with the switch and disconnects the warning light!  This is what happened on my Mustang!!!

Just proves what can go wrong will go wrong. Man I hope this is it.

LCJUTILA 

LCJ,

Yeah, I thought about that, but it seems to me it would affect both fronts, whereas this car has consistently had the right front in trouble. My head aches and we have a dinner engagement. I'm outa here for now. When I get back I'm gonna try and stay up almost all night for the F1 race. Wish me luck. My wife will probably find me slumped in the recliner drooling like Homer Simpson in the morning. (Not a pretty image, eh?)

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Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill-

Is it a diagonal braking system? Right front left rear?

LCJ 

Zach-

Read through the entire posting and did not see anything about how the brakes worked prior to doing any of this stuff when the original leaking master cylinder was in the car. Also, was it a dirty mess under the hood when you started?  (No offense) Maybe a more polite way of putting the question would be is there any chance dirt got into the master cylinder during installation?  Some old repair manuals talk about dirt in the master cylinder causing the brakes to bind because of a clogged bypass valve inside the master cylinder or the pedal to be spongy because of same.  Both are symptoms you describe. Anyway, to me it seems the two things that cause brake problems besides wear are Dirt and Leaks.

Don't worry, when you figure this thing out the brakes will be so fresh you will probably be able to get the thing to stand on its nose!

LCJUTILA 

Motorbill and LCJUTILA,

Thanks for hanging in there with me on this one.

One thing that I thought was insignificant, but upon reflection might be more serious, is the brake failure switch (item 40 in the Moss catalog) on the bottom of the brake master cylinder.  After installing the new master cylinder, the brake light would not go off.  I replaced the new switch with the old, and the light went off, causing me to believe that the new switch was defective.  Could that be part of the problem?

The engine compartment was relatively clean - albeit, butchered - when I bought the car.  And, as a former aircraft mechanic, I took special care to avoid getting dirt in the lines when installing the new master cylinder.

I don't know.....

zach